Restore os_CODENAME for old rhel distros

With [1] fips based jobs which runs on 9-stream started
to fail as os_CODENAME not applicable on those. This
patch adds fallback as before.

Moving fips jobs to 10-stream/rocky requires some more work
due to [2]

[1] https://review.opendev.org/c/openstack/devstack/+/960342
[2] https://fedoraproject.org/wiki/Changes/RemoveFipsModeSetup

Change-Id: I6d7ba4f5698e9b4837b29662b0b7f883b3c5de35
Signed-off-by: Yatin Karel <ykarel@redhat.com>

functions-common

@@ -440,7 +440,7 @@ function GetOSVersion {
     source /etc/os-release
     if [[ "${ID}" =~ (centos|rocky|rhel) ]]; then
         os_RELEASE=${VERSION_ID}
-        os_CODENAME=$(echo $VERSION | grep -oP '(?<=[(])[^)]*')
+        os_CODENAME=$(echo $VERSION | grep -oP '(?<=[(])[^)]*' || echo 'n/a')
         os_VENDOR=$(echo $NAME | tr -d '[:space:]')
     else
         _ensure_lsb_release